The present invention relates generally to methods for releasing a micro-electronic device from a handle substrate, and more specifically to stiction resistant methods for releasing a micro-electronic device from a handle substrate.
Extraordinary advances are being made in micro-mechanical devices and micro-electronic devices, including micro-electro-mechanical devices (MEMs), which comprise integrated micro-mechanical and micro-electronic devices. The terms “micro-electronic device” and “micro-assembly” are used generically herein to encompass micro-electronic components, micro-mechanical components, MEMs components and assemblies thereof. Generally, micro-electronic device have feature dimensions that are less than about 1000 microns. The present disclosure also relates to nano-electronic devices, including nano-electro-mechanical devices (NEMs), which may have feature dimensions that are less than about 10 microns.
Many micro-electronic devices are initially formed on a silicon-on-insulator (SOI) substrate. An SOI substrate generally comprises an oxide or other insulator layer formed on a handle substrate. The handle substrate is generally employed as a physical interface for wafer transportation, orientation and alignment during and after manufacturing. The insulator layer may have a thickness ranging between about 500 nm and about 5000 nm, and is often (although not necessarily) employed as a sacrificial layer. The SOI substrate also includes a silicon or other semiconductor layer formed on the insulator layer. The micro-electronic devices are generally formed in the silicon layer, such that completed devices can be separated (released) from the SOI substrate by etching the insulator layer underlying the completed devices.
Typically, the insulator layer is removed by a wet etch process, such as one employing an HF etchant chemistry. A rinsing agent, such as de-ionized water (DI water), is then used to flush the entire article, thereby arresting the etching process and at least partially removing residue and contaminants left by the etching process. An active or passive drying process is then performed. However, when the rinsing agent dries between the handle substrate and micro-electronic devices, stiction may occur, causing the micro-electronic devices to adhere to each other and the handle substrate. Such adhesion may be caused by surface tension, van der Waals and/or electrostatic attraction. The adhesive force resulting from stiction between the micro-electronic devices and the handle substrate is often greater than the forces that the micro-electronic devices can structurally withstand. As such, the force required to release the micro-electronic devices from the handle substrate, or the force required to overcome the stiction, is likely to damage the micro-electronic devices. Moreover, proposed solutions to overcome stiction, including the use of a drying gas such as CO2 or a highly evaporative liquid such as glycol or methanol, do not satisfactorily alleviate stiction.
Accordingly, what is needed in the art is a method of releasing a micro-electronic device from a substrate that addresses the above-discussed issues of the prior art.